What do you exactly mean by "build quality"? Are you saying it'll suddenly blow up in your hand?Ions=waste of time and money!
Seriously, for a good first marker get something half decent 2nd hand off of these forums. something like a Ego 05 or PM/DM, you are looking at £300 max for these markers.
Ions are pigs to maintain and the build quality is low. At least if you get, say, an Ego 05 you know that it will be really good quality because it was one of the best when it was released, With the Ion you get something new with poor stats and quality.
***let the flaming commence***
The main reason Ion's are so cheap is because of the Economies of scale. That's what SP were banking on.